Supplemental power supply for a battery-powered device

ABSTRACT

A battery-powered device, such as a motorized window treatment, may provide power to an electrical load, such as a motor. The device may also include a control circuit and a communication circuit. In addition to the battery, the device may be configured to receive power from a supplemental power source, such as a solar cell or wireless RF power supply, through which to power the control and communication circuits. The device may include a voltage monitor and a switch to intelligently control whether the battery or the supplemental power source is powering the control and communication circuits.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/240,444, filed on Jan. 4, 2019, which claims the benefit of U.S.Provisional Patent Application No. 62/614,060, filed Jan. 5, 2018, theentire disclosures of which are hereby incorporated by reference herein.

BACKGROUND

A control device may include control and communication circuitry, suchas wireless communication circuitry, for receiving control instructionsfrom an external device or network to control the control device. Thecontrol device may also include one or more batteries for poweringelectrical circuitry of the control device, for example, the control andcommunication circuitry. The batteries may also be used to power otherelectrical circuits associated with the control device, for example, amotor, light-emitting diode indicators, etc. The battery lifetime of thecontrol device may primarily depend on how frequently the otherelectrical circuits of the control device are used. For electricalcircuits of control devices that are used infrequently (e.g., once ortwice per day), the power drain of control and communication circuitrymay contribute to a significant portion of the battery energy usagesince the communication circuitry may need to periodically check for newcontrol instructions. For example, a motorized window treatment may onlyraise and/or lower a shade fabric once or twice per day, but the controland communication circuitry may consume power periodically throughoutthe entire day as the communication circuitry checks for new controlinstructions and wakes up the control circuit when control instructionsare received. In some cases, the control and communication circuitry mayuse up to 50% or more of the battery capacity over the lifetime of thebatteries, even with the use of energy consumption mitigationtechniques, such as low-power sleep mode for the control andcommunication circuitry.

To extend battery life, battery-powered control devices may rely onphotovoltaics to charge rechargeable batteries using solar energy.However, rechargeable batteries typically have limited cyclinglifetimes. Additionally, solar charging methods are not optimal forrechargeable batteries, which further limits cycling lifetimes.Therefore, an alternative supplemental power supply for abattery-powered wireless device is needed.

FIG. 1 is a simplified block diagram of an example prior art motorsupply drive circuit 100 that may be situated in a space, such as aroom. The motor supply drive circuit 100 may contain a motor 106, whichmay be used to control the position of a covering material (e.g., afabric) of a motorized window treatment (not shown) based on controlinstructions from a control and communication circuit 108. The controland communication circuit 108 may receive wireless control instructionsfrom an external control device (not shown) via a network for example.The motor 106 may draw supply voltage V_(CC1), supplied by arechargeable battery 104, to control the position of the fabric of themotorized window treatment based on the received control instructions.For example, the rechargeable battery 104 may supply 12 volts (V) to themotor 106.

The control and communication circuit 108 may receive power from therechargeable battery 104 through a power supply (e.g., a buck convertercircuit 110). The buck converter circuit 110 may generate a supplyvoltage V_(CC2). The buck converter circuit 110 may reduce the batteryvoltage V_(CC1) to a magnitude suitable to power the control circuitry.For example, the buck converter circuit 110 may reduce the batteryvoltage V_(CC1) received from the rechargeable battery from 12V to 3V topower the control circuit 108.

The rechargeable battery 104 may be charged externally through a wiredconnection, such as power supply connected to an AC wall outlet forexample, or alternatively, through a solar cell 102. The solar cell 102may harvest light energy from light external to the space (e.g., fromdaylight), and/or the solar cell 102 may harvest light energy from lightinternal to the space (e.g., from the artificial lights).

While the light energy harvested by the solar cell may be used to extendthe battery life by charging the rechargeable battery 104, thisconfiguration may have several disadvantages. First, rechargeablebatteries may not be optimally suited for being charged byphotovoltaics. The nature of solar cell energy generation, which isproduced as a trickle charge of current, may reduce the useable lifetimeof the rechargeable battery. Secondly, rechargeable batteries are morecostly than traditional single-use batteries.

SUMMARY

In one aspect, the present disclosure relates to a supplemental powersupply for a battery-powered load control device and to a method ofsupplying power to the load control device from the supplemental powersupply which increases the battery life. The supplemental power supplymay be based on renewable but unreliable energy sources such aselectromagnetic, acoustic, mechanical, thermal, or other types ofsources. The supplemental power supply may provide power just to thecontrol circuit and communication circuits for example, while thebattery provides power to a larger transient load. While the embodimentsherein specifically describe motorized window treatments, one skilled inthe art will recognize that the supplemental power supply describedherein may be applied generally to any battery-powered load controldevice in order to increase the battery lifetime.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a block diagram of an example prior art motor supply drivewith a rechargeable battery and solar cell.

FIG. 2 shows a block diagram of an example device with a battery andsupplemental power source.

FIG. 3 is an example voltage profile over time of an energy storagedevice powered by a solar cell.

FIG. 4 is an example schematic of a voltage monitor and switch.

FIG. 5 is an example block diagram of a device with a battery andsupplemental power source according to an embodiment.

FIGS. 6A, 6B, and 6C are example methods which may be executed by one ormore monitor circuits to control the input and output switches, and toenable and disable a power converter circuit.

FIG. 7A is an example graph of voltage over time on the first and secondenergy storage devices with respect to the methods shown in FIGS. 6A,6C.

FIG. 7B is an example graph of voltage over time on the first and secondenergy storage devices with respect to the methods shown in FIGS. 6A,6B.

FIG. 8 is an example schematic based on the block diagram of FIG. 5.

FIG. 9 shows an example user environment with a wireless power supplysource for a motorized window treatment.

FIG. 10 shows an example supplemental power supply based on radiofrequency (RF) signals.

FIG. 11 shows a block diagram of an example device with a battery andsupplemental power source according to an alternate embodiment.

FIG. 12 is an example voltage profile over time of an energy storagedevice and a battery according to the embodiment described in FIG. 11.

DETAILED DESCRIPTION

As described herein, a load control device may receive power from afirst, or primary power source, such as a battery, and deliver powerderived from the primary source to power one or more electrical loads.The load control device may be further configured to receive power froma second, or supplemental power source. The load control device may beconfigured such that the supplemental power source is an optional powersource. For example, the supplemental power source may be externallyconnected to the load control device. Alternatively, the load controldevice may be configured such that the supplemental power source isintegrated with the load control device.

FIG. 2 is a block diagram of an example device 200. Device 200 mayinclude at least a first electrical load 206 and a second electricalload 225. The second electrical load 225 may include a control circuit208 and/or a communication circuit 226, although one will recognize itmay include fewer and/or additional and/or other circuit components. Asone example, the second electrical load may operate at power voltage(s)lower than that of the first electrical load. In this respect, thesecond electrical load may be referred to herein as low voltagecircuitry. As one example, device 200 may be a load control device andin particular, may be configured as a motor supply drive circuit. Inthis configuration, the electrical load 206 may include one or moremotors and corresponding motor supply drive circuitry. The motor 206 maybe coupled to a roller tube or a drive shaft (not shown) of a motorizedwindow treatment for controlling the position of a covering material(e.g., a fabric) of the motorized window treatment. For example, themotor may be a direct-current (DC) motor, which may operate at a DCmotor voltage of 12 volts (V). Typical DC motor voltages may be in therange of 9V to 24V, although other voltages are possible. For purposesof description, device 200 will be described herein as a motor supplydrive circuit that includes a motor as electrical load 206 that isconfigured to control a motorized window treatment. Nonetheless,electrical load 206 may be a load different from a motor, for example,electrical load 206 may include one or more electrical loads, and device200 may be a device other than a motor supply drive circuit. Forexample, the electrical load 206 may be a sensor circuit, such as anoccupancy sensor, ambient light sensor, accelerometer, etc. Although themotor 206 and electrical load 225 are shown as part of device 200, onewill understand that motor 206 and/or electrical load 225 do need not bepart of device 200 but may be external to the device 200.

The control circuit 208 may control an amount of power provided to theelectrical load 206, i.e., the motor. The motor (electrical load 206) ofdevice 200 may control or adjust the position of the covering materialof the motorized window treatment in response to one or more controlsignals received from the control circuit 208. The control circuit 208may include one or more of a processor(s) (e.g., a microprocessor(s)), amicrocontroller(s), a programmable logic device(s) (PLD), a fieldprogrammable gate array(s) (FPGA), an application specific integratedcircuit(s) (ASIC), or any suitable processing device or combinationthereof. The second electrical load 225 of device 200 may also includeone or more memory modules (“memory”) (not shown), including volatileand/or non-volatile memory modules, that may include non-removablememory modules and/or a removable memory module. The memory may becommunicatively coupled to the control circuit 208. Non-removable memorymay include random-access memory (RAM), read-only memory (ROM), a harddisk, or any other type of non-removable memory storage. Removablememory may include a subscriber identity module (SIM) card, a memorystick, a memory card, or any other type of removable memory. The memorymay store one or more software based control applications that includeinstructions that may be executed by the control circuit 208. Thecontrol circuit 208, when executing such instructions, may performsignal coding, data processing, power control, input/output processing,and/or any other functionality that enables the control circuit 208 toperform as described herein.

The control circuit 208 may receive messages from the communicationcircuit 226. The communication circuit 226 may be a wired and/or awireless communication circuit. For example, the communication circuit226 may include a radio-frequency (RF) transceiver coupled to an antennafor transmitting and/or receiving RF signals. The communication circuit226 may communicate via a Wi-Fi communication link, a Wi-MAXcommunications link, a Bluetooth® communications link, a ZigBee® link, anear field communication (NFC) link, a cellular communications link, atelevision white space (TVWS) communication link, a proprietary protocol(e.g., the ClearConnect® protocol), or any combination thereof. Thecommunication circuit 226 may receive messages from an external controldevice (e.g., a remote control device) via any of these protocolsdescribed herein.

The communication circuit 226 may be operatively connected to thecontrol circuit 208. The control circuit 208 may generate controlsignals for controlling the motor 206 based on the received messages.For example, the communication circuit 226 may receive messages from theexternal control device. The messages may be received by thecommunication circuit 226 through a wired or wireless communicationlink. For example, a remote control device may wirelessly send a commandmessage to raise the fabric of the motorized window treatment to thecommunication circuit 226, and the control circuit 208 may control themotor 206 to raise or lower the fabric based on the received command. Asanother example, the control circuit may execute instructions (e.g., atimeclock schedule) and control the motor 206 to raise or lower thefabric independently of received messages via communications circuit226.

Although communications have been described as a function of thecommunication circuit 226, one skilled in the art will readilyunderstand that the communication circuit may alternatively and/oradditionally be integrated with the control circuit to achieve the sameeffect.

The first electrical load/motor 206, and the second electrical load 225consisting of the communication circuit 226 and the control circuit 208,for example, may be powered by a battery 204 that provides a batteryvoltage V_(BATT). The battery 204 may be a single-use battery.Alternatively, the battery 204 may be a rechargeable battery. Thebattery 204 may be a single battery or it may be a battery packincluding multiple batteries connected in series, for example. Thebattery/batteries of the battery pack may be configured to providesufficient voltage for powering the motor. For example, when battery 204is a battery pack it may include eight D-cell batteries coupled inseries to provide 12 volts to the motor. The device 200 may include abattery housing into which one or more batteries may be inserted orconnected to.

The battery 204 may power the control circuit 208 and the communicationcircuit 226 of the second electrical load 225 through a controllableswitch 214. The battery 204 may provide power to the second electricalload 225 when the controllable switch 214 is in a first position orfirst state. A power converter circuit 216, such as a buck convertercircuit, may be placed in series between the control and communicationcircuits 208, 226 and the controllable switch 214, as shown.Alternatively, the power converter circuit 216, that is, a buckconverter circuit, may be placed in series between the battery 204 andthe switch 214 to reduce the battery voltage V_(BATT) for providingpower to the control circuit 208 and the communication circuit 226(e.g., at location A in FIG. 2). For example, the battery voltageV_(BATT) from the battery 204 may be 12 volts to run the motor 206, andthe power converter circuit 216 may reduce the battery voltage V_(BATT)to a lower DC supply voltage V_(CC), such as 3 volts, to power thecontrol circuit 208 and the communication circuit 226. The powerconverter circuit 216 may be a switching power supply or other suitablecircuitry to down-regulate the voltage with a high efficiency ofconversion. For example, chip TSP62120 manufactured by Texas Instrumentsis an example step-down converter chip with 96% efficiency that may beused. A linear regulator may alternatively be used to reduce thevoltage; however, low power efficiency during the voltage conversion mayshorten the battery life.

Alternatively, motor supply drive circuit 200 may not include powerconverter circuit 216 such that the battery voltage V_(BATT) may becoupled directly to the control circuit 208 and the communicationcircuit 226 via switch 214. In this configuration, motor supply drivecircuit 200 may include a boost circuit (not shown) though which themotor 206 may be supplied with voltage. The boost circuit may be coupledin series between the battery 204 and the motor 206 (e.g., at location Bin FIG. 2). For example, the battery 204 may provide the battery voltageV_(BATT) to the control circuit 208 and the communication circuit 226 ata low magnitude, and the boost circuit may generate a boosted voltagefrom the battery voltage V_(BATT), where the boosted voltage has amagnitude appropriate to run the motor 206, e.g., 12V. The low magnitudeof the battery voltage V_(BATT) may be in the range of 1-5 volts. Forexample, the control and communication circuits 208, 226 may be poweredby a low voltage of 3.3V. One will recognize that other configurationsare possible.

Additionally, although not shown, one will understand that the device200 may include one or more additional batteries, i.e., a backupbattery, which may be used for running a date/time clock and/or thememory to maintain the memory in case of a failure of the primary powersource (that is, battery voltage V_(BATT) is insufficient to power theone or more electrical loads 206, 225).

The motor supply drive circuit 200 may additionally include asupplemental power supply 220. The supplemental power supply 220 maygenerate supplemental voltage V_(SUPP) for powering the secondelectrical load 225, here the control circuit 208 and the communicationcircuit 226. The communication circuit 226 may periodically wakeup tolook for control commands, and/or the control circuit 224 may runtimers, etc., which may consume power from the supplemental power supply220. The supplemental power supply 220 may alleviate the power drawburden of the control circuit 208 and the communication circuit 226 onthe battery 204. In this way, the supplemental power supply 220 maysubstantially increase the lifetime of the battery 204. For example, ifthe battery 204 of the motor supply drive circuit 200 is a battery packhaving eight D-cell batteries coupled in series and the motor supplydrive circuit 200 lowers and raises a shade fabric that is three feetwide by five feet long twice a day, battery 204 may have a lifetime ofapproximately three years. If the same motor supply drive circuit 200(e.g., having the same battery pack and operating under the sameconditions) includes the supplemental power supply 220, the battery mayhave an extended lifetime of over seven years.

The supplemental power supply 220 may be connected to the motor supplydrive circuit 200 via a terminal 224. The terminal 224 may be a circuittrace or a mechanical contact, such as a terminal block, wire connector,metal contact pad, or any other suitable mechanical contact mechanism.The supplemental power supply 220 may be integrated with the motorsupply drive circuit 200 (e.g., in the same enclosure), or thesupplemental power supply may be an additional power supply optionallyprovided to a user and installed externally to the motor supply drivecircuit 200 by the user. The supplemental power supply 220 may beprovided externally to the motor supply drive circuit 200 to reduce costof the motor supply drive circuit for users who do not require thesupplemental power source. When supplying power to the control circuitand the communication circuit, the supplemental power source may providea sufficient amount of power for the control circuit to provide commandsto the electrical load. For example, the control circuit may send one ormore control commands to the electrical load 206, i.e., the motor, whilethe control circuit is powered by the supplemental power supply.

The supplemental power supply 220 may include a supplemental powersource 202. The supplemental power supply 220 may additionally includean energy storage device 212. The energy storage device 212 may storeenergy provided by the supplemental power source 202, and provide thesupplemental voltage V_(SUPP). In one embodiment, the energy storagedevice 212 may be a super capacitor. For example, the super capacitormay be an electric double-layer capacitor (ELDC), an ultracapacitor, ora Goldcap. The supercapacitor may have a capacitance of several tens offarads in order to store sufficient charge from the supplemental powersource 202. For example, the supercapacitor may have a capacitance of 50farads (F) and may store, on average, 200 joules (J) of energy per day.One will recognize other examples are possible. For example, the energystorage device may be another type of capacitor, such as a tantalum orelectrolytic capacitor; a rechargeable battery; or any other type ofenergy storage device.

The supplemental power source 202 may be a renewable power source. As aresult, the supplemental supply voltage V_(SUPP) generated by thesupplemental power supply 220 may be unreliable. For example, thesupplemental power source 202 may be one or more solar cell(s) orphotovoltaic (PV) cell(s), that is, a PV module. The power provided bythe PV cell(s) to charge the energy storage device 212 may depend on theintensity, frequency, and duration of light provided to the PV cell(s).For example, the PV cell(s) may not charge the energy storage device 212at night after sunset.

The PV cell(s) may be made of amorphous or crystalline silicon, organicphotovoltaic materials, or any other any suitable photovoltaic material.The PV cell(s) may be characterized by an optimal voltage at which poweris transferred at a maximum efficiency. For example, a PV moduleconstructed of six amorphous silicon cells with a total active area ofapproximately 34 mm by 142 mm may generate a current of 5 milliamperes(mA) with indirect sunlight when the cell is maintained with an outputvoltage of 5V.

As another and/or additional example, the supplemental power source 202may be a wireless power supply. The wireless power supply may include areceiver such as an antenna which receives electromagnetic energy from aremotely located transmitter. For example, a power transmitter may beplugged into an electrical outlet and transmit power from the electricaloutlet via a transmit antenna within the power transmitter. The wirelesspower supply may have a receive antenna corresponding to the transmitantenna which receives power from the power transmitter and stores theenergy in the energy storage device 212. Wireless power supplies formotorized window treatments are described in more detail in U.S. patentapplication Ser. No. 15/471,991, filed Mar. 31, 2017, entitled “WirelessPower Supply for Electrical Devices”, the entire disclosure of which isherein incorporated by reference. Other example wireless power suppliesare possible.

As another and/or additional example, the supplemental power source 202may be any other suitable receiver that receives energy from theenvironment and converts the energy to electrical power. For example,the supplemental power source 202 may receive electromagnetic, acoustic,mechanical, thermal, or other types of energy from the environment andharvests this energy to provide electrical power to charge the energystorage device 212.

Due to the unreliable nature of the supplemental power source 202 (e.g.,if light is not present to power the PV cell(s)) and/or if thesupplemental power supply 220 is an optional supply that may notinstalled to the motor supply drive circuit 200, the motor drive supplycircuit 200 may include a monitor circuit 218 for monitoring anddetermining the magnitude of the supplemental supply voltage V_(SUPP)before power may be provided to the control circuit 208 and thecommunication circuit 226 via connection 224 from the supplemental powersupply 220. The supplemental supply voltage V_(SUPP) provided by thesupplemental power supply 220 may power the control circuit 208 and thecommunication circuit 226 through the controllable switch 214. When thesupplemental power supply 220 is installed, the monitor circuit 218 maydetect or determine whether the magnitude of the supplemental supplyvoltage V_(SUPP) is a suitable magnitude to be coupled to the powerconverter circuit 216. When the monitor circuit 218 detects ordetermines that the magnitude of the supplemental supply voltageV_(SUPP) is a suitable magnitude, it may control the switch 214 to thesecond position, thereby connecting the supplemental supply voltageV_(SUPP) to the power converter circuit 216. The switch 214 may receivethe control command from the monitor circuit 218 and the switch may thendisconnect the battery voltage V_(BATT) supplied by the battery 204 tothe control circuit 208 and communication circuit 226 to allow thecontrol circuit and communication circuit to be powered from thesupplemental supply voltage V_(SUPP) provided by the supplemental powersupply 220.

When the monitor circuit 218 detects or determines that the magnitude ofthe supplemental supply voltage V_(SUPP) is not a suitable magnitude(e.g., because the supplemental power supply 220 is not present orbecause the energy storage device 212 is not sufficiently charged), themonitor circuit 218 may control the switch 214 to connect the batteryvoltage V_(BATT) from the battery 204 to the power converter circuit216. The switch 214 may receive the control command from the monitorcircuit 218 and the switch may then return to the first position (e.g.,the first state), thereby disconnecting the supplemental supply voltageV_(SUPP) supplied by the supplemental power supply 220 to the controlcircuit 208 and communication circuit 226 to allow the control circuitand communication circuit to be powered from the battery voltageV_(BATT) provided by the battery 204.

As one example, the monitor circuit 218 may be a voltage monitorcircuit. The monitor circuit 218 may monitor the supplemental supplyvoltage V_(SUPP) using a comparator or other suitable analog circuitry.In the case where the power converter circuit 216 is located at locationB (i.e., the battery 204 may directly power the electrical load 225),for example, the monitor circuit 218 may compare the magnitude of thesupplemental supply voltage V_(SUPP) with the magnitude of the batteryvoltage V_(BATT) provided by the battery 204. When the magnitude of thesupplemental supply voltage V_(SUPP) is less than the magnitude of thebattery voltage V_(BATT) for example, the monitor circuit 218 maycontrol the switch 214 such that the battery voltage V_(BATT) from thebattery 204 is provided to the control circuit 208 and communicationcircuit 226 (i.e., maintaining the switch 214 in the first position).When the magnitude of the supplemental supply voltage V_(SUPP) isgreater than or equal to the magnitude of the battery voltage V_(BATT)or example, the monitor circuit 218 may control the switch 214 such thatthe supplemental supply voltage V_(SUPP) from the supplemental powersupply 220 is provided to the control circuit 208 and communicationcircuit 226. One will recognize that other configurations are possible.For example, when the power converter circuit 216 is located in positionA of FIG. 2, the output of the power converter circuit 216 (as opposedto V_(BATT)) may be compared with V_(SUPP).

According to another example, where the power converter circuit 216 isconnected as shown in FIG. 2 between the switch 214 and the electricalload 225, the monitor circuit 218 may include a clamp circuit and alatch circuit. The monitor circuit 218 may operate to maintain themagnitude of the supplemental supply voltage V_(SUPP) of thesupplemental power supply 220 within a certain range. The monitorcircuit 218 may maintain the input voltage to the power convertercircuit 216 above a minimum threshold and/or below a maximum threshold.For example, the monitor circuit 218 may compare the magnitude of thesupplemental supply voltage V_(SUPP) to the minimum and maximumthresholds. When the monitor circuit 218 determines that the magnitudeof the supplemental supply voltage V_(SUPP) reaches and/or is above amaximum threshold, the latch circuit may engage, causing monitor circuit218 to configure the switch 214 (e.g., turn the switch to the secondstate, or on state, i.e., to the second position) to provide power tothe power converter circuit 216 from the supplemental power supply 220.The latch circuit may remain engaged until the magnitude of thesupplemental supply voltage V_(SUPP) reaches and/or falls below aminimum threshold, wherein the latch circuit of the monitor circuit 218may disengage, thereby causing monitor circuit 218 to configure theswitch 214 (e.g., turning the switch to the first state, or off state,i.e., to the first position) to provide power to the power convertercircuit from the battery 204.

Additionally, when the monitor circuit 218 determines that the magnitudeof the supplemental supply voltage V_(SUPP) reaches and/or is above themaximum threshold, the clamp circuit of monitor circuit 218 may clampthe supplemental supply voltage V_(SUPP) to not exceed the maximumthreshold.

The maximum and minimum thresholds may be selected to ensure that thesupplemental power source 202 operates in a region of maximum powertransfer. For example, assuming the supplemental power source is anamorphous silicon solar cell as described above, it may operate mostefficiently around 5V. Therefore, the maximum threshold may be set closeto, for example 5V (e.g., 4.9V). When used in conjunction with a 50farad supercapacitor for energy storage device 212, monitor circuit 218may operate to ensure that the output voltage V_(SUPP) of thesupercapacitor does not drop below a minimum threshold of 4.2V, forexample, to maximize the efficiency of the solar cell. If the outputvoltage drops below the minimum threshold, the monitor circuit 218 maycontrol the switch 214 to power the control circuit 208 and thecommunication circuit 226 from the battery 204 (e.g., rather than theenergy storage device 212).

Although the monitor circuit 218 has been described herein as a voltagemonitor, one skilled in the art will recognize that other types ofmonitor circuits may be used. For example, a coulomb counter mayalternatively be used as a monitor of current being supplied by thesupplemental power supply 220.

The switch 214 may include an electronic switch or transistor, such as afield-effect transistor (FET) or bi-polar junction transistor (BJT).

FIG. 3 is an example profile 300 of a magnitude of a supply voltageV_(SUPP) developed across an energy storage device, such as asupercapacitor, over time when powered by a solar cell or photovoltaiccell. For example, the photovoltaic cell may provide a maximum powertransfer to the energy storage device at a voltage around 5 volts.Deviations from this optimal voltage may cause decreased efficiency inenergy transfer from the photovoltaic cell to the energy storage device212. Therefore, the magnitude of the supply voltage V_(SUPP) may becontrolled by circuitry (e.g., the monitor circuit 218 and the switch214) to maintain the magnitude of the supply voltage between a maximumthreshold Vmax and a minimum threshold Vmin. The maximum and minimumvoltage thresholds Vmax, Vmin may ensure that maximum power transferfrom the photovoltaic cell to the energy storage device is achieved.

The photovoltaic cell may begin charging when sunlight, for example, isincident on the photovoltaic cell during the morning of Day 1, shown at302. The current generated by the photovoltaic cell may begin chargingthe energy storage device 212. As described previously, according tothis example when the voltage of the energy storage device reaches themaximum threshold Vmax (e.g., the maximum threshold as set by themonitor circuit 218) at 304, the monitor circuit 218 may latch and clampthe magnitude of the supply voltage at the maximum threshold Vmax. Whenthe latch engages, the switch circuit 214 may change states to thesecond position to provide power from the energy storage device 212 tothe power converter circuit 216, and the battery 204 may no longerprovide current to the power converter circuit.

As the amount of sunlight begins to decrease at the end of Day 1, themagnitude of the supply voltage V_(SUPP) on the energy storage device212 may also decrease as shown at 306, as the power converter circuit216 continues to draw power from the energy storage device. While themagnitude of the supply voltage on the energy storage device remainsabove the minimum threshold Vmin, the latch and switch may remainengaged, and the power converter circuit 216 may continue to receivepower from the energy storage device.

During Day 2, as sunlight incident on the photovoltaic cell increases,the magnitude of the supply voltage V_(SUPP) on the energy storagedevice 212 may reach a maximum level at 308. If it is cloudy outside,the magnitude of the supply voltage on the energy storage device may notreach the maximum threshold Vmax, and the clamp circuit may not engage.However, because the magnitude of the supply voltage is maintained abovethe minimum threshold Vmin, the latch circuit may still be engaged andthe switch may continue to provide power from the energy storage device212 to the power converter circuit. Therefore, the battery 204 may notprovide power to the power converter circuit at this point 308.

As sunlight incident on the photovoltaic cell decreases, the energystorage device 212 may continue to discharge, and the magnitude of thesupply voltage V_(SUPP) on the energy storage device 212 may reach theminimum threshold at 310. According to this example, when the magnitudeof the supply voltage V_(SUPP) on the energy storage device 212 fallsbelow the minimum threshold Vmin, the latch circuit of the monitorcircuit 218 may unlatch, thereby causing the switch 214 to change stateto the first position, thereby connecting the power converter circuit tothe battery 204, and not the energy storage device 212.

The switch 214 may remain in this position (i.e., connecting the powerconverter circuit 216 to the battery 204) as the magnitude of the supplyvoltage V_(SUPP) on the energy storage device 212 increases when thephotovoltaic cell charges the energy storage device again. The switch214 may not be coupled to provide power from the energy storage device212 to the power converter circuit 216 until the magnitude of the supplyvoltage V_(SUPP) on the energy storage device once again reaches, forexample, the maximum threshold Vmax, thereby turning on the clamp andlatch circuits and configuring the switch to supply power from theenergy storage device 212.

During the majority of the lifetime of the device 200, the latch circuitmay remain engaged and the switch 214 may provide power to the powerconverter circuit via the energy storage device 212. For example, theenergy storage device may provide power to the power converter circuitover 95% of the lifetime of the device. The monitor circuit 218 mayswitch over to powering the power converter circuit by the battery 204only after several days of low sunlight availability.

FIG. 4 shows a device 400 which is an example implementation of device200 of FIG. 2 with the monitor circuit 218 (in this example a voltagemonitor circuit) and switch 214 depicted in schematic form together withthe battery 204. Device 400 further includes the components of FIG. 2such as the supplemental power source 202 (shown in this example asphotovoltaic cell 405), the energy storage device 212 (e.g., shown inthis example as energy storage device 412 and consisting ofsupercapacitors C2, C4), the power converter circuit 216, and the firstelectrical load 206, and the second electrical load 225. The circuitshown may set the impedance for the photovoltaic cell 405. Voltage tothe second electrical load 225 (e.g., control circuit 208, communicationcircuit 226, and/or other low voltage circuitry) is provided by thepower converter circuit 216, which reduces the voltage from the battery204 or energy storage device 412 to the appropriate level for poweringthe second electrical load 225 as described previously.

All voltages described in FIG. 4 are measured with reference to circuitcommon, shown as 406 in FIG. 4. The battery 204 may or may not providevoltage to the power converter circuit 216 based on the state of ap-channel metal oxide semiconductor field-effect transistor (PMOS FET)Q3. For example, the battery 204 may provide voltage to the powerconverter circuit 216 when FET Q3 is conductive. The FET Q3 may berendered conductive to provide the battery voltage V_(BATT) from thebattery 204 when the energy storage device 412 does not have sufficientcharge to provide power to the power converter circuit 216, e.g., whenthe magnitude of the supplemental supply voltage V_(SUPP) stored by theenergy storage device 412 is below a minimum threshold.

The photovoltaic cell 405 may generate a voltage and a current whenexposed to light. When voltage is generated by the photovoltaic cell405, an NPN bipolar junction transistor (BJT) Q5, for example, may beginto conduct current, charging the supercapacitors C2, C4. A resistor R7may be placed between the collector and the base of the transistor Q5.In order for the transistor Q5 to conduct current through thecollector-emitter junction (e.g., “turn on” the transistor), theresistance of a resistor R7 should be selected to be a sufficientlysmall value to cause the base-collector junction of the transistor Q5 tohave only a small reverse bias, allowing the transistor Q5 to beself-driven. For example, the resistor R7 may have a value of about 700ohms.

As the voltage generated by the photovoltaic cell increases and exceedsthe maximum threshold Vmax, the clamp circuit comprised of, for example,a PNP bipolar junction transistor (BJT) Q7, an adjustable shuntregulator VR1, a resistor R1, and a resistor R3 of the voltage monitorcircuit may act to throttle the current conducted through the transistorQ5. The clamp circuit may slow the rate of charge of the supercapacitorsC2, C4 through the transistor Q5 by changing the impedance of Q5 andturning on the transistor Q7 to split the path of the current providedby the photovoltaic cell. The current through transistor Q7 may belimited by resistor R11, while the current through the adjustable shuntregulator VR1 may be primarily set by the voltage drop across thebase-emitter junction of transistor Q7 (i.e., the voltage drop acrossresistor R5). Transistor Q5 may increase in impedance to allow theminimum current required to maintain the clamp voltage, therebydecreasing the output current from the photovoltaic cell 405 provided tosupercapacitors C2, C4.

For example, as the voltage of the photovoltaic cell increases, thevoltage developed across the resistors R1, R3 may also increase. Thevoltage at the junction 402 of the resistors R1 and R3 may set thereference voltage input provided to the adjustable shunt regulator VR1.The reference voltage input may set the breakdown voltage threshold ofthe adjustable shunt regulator VR1. The resistance values of theresistors R1, R3 may be selected to provide an appropriate breakdownvoltage threshold at the junction 402 of the resistors R1, R3 for theadjustable shunt regulator VR1. For example, the breakdown voltagethreshold may be 1.25 volts.

For example, the adjustable shunt regulator VR1 may be part numberTLV431 manufactured by Texas Instruments. The adjustable shunt regulatorVR1 may regulate the supplemental supply voltage V_(SUPP) on thesupercapacitors by controlling the current generated by the photovoltaiccell through the transistor Q5. When the photovoltaic cell voltagegenerated by the photovoltaic cell exceeds the maximum threshold, thevoltage at the junction of R5 and VR1 may exceed the breakover voltageof the adjustable shunt regulator VR1, as set by the resistors R1 and R3at node 402. The adjustable shunt regulator VR1 may then begin toconduct current from the base of the transistor Q7 to circuit common 406while clamping the voltage to the maximum threshold. When the adjustableshunt regulator VR1 conducts current from the base of the transistor Q7,transistor Q7 may turn on and begin conducting current. The transistorQ7 may draw base current away from transistor Q5, causing Q5 to operatein a linear mode. When Q5 operates in a linear mode, the impedancebetween the collector-emitter may increase to limit the charging currentfrom the photovoltaic cell to the supercapacitors, thereby clamping thevoltage and maintaining the supplemental supply voltage at or below themaximum threshold Vmax. As the current through the transistor Q5 isreduced, the transistor Q5 may operate in its linear active region,providing a high impedance to the photovoltaic cell and reducing thecurrent flow from the photovoltaic cell to charge the supercapacitorsC2, C4.

When the transistor Q7 begins to conduct current, the current flow maytrigger an NPN bipolar junction transistor Q11, for example, to alsobegin conducting current. The transistor Q11, together with, forexample, a PNP bipolar junction transistor Q9, a resistor R9, a resistorR13, and a capacitor C6, may operate as a latch circuit. When the clampcircuit engages the latch circuit, the latch circuit may act to maintainQ3 in the off state until the voltage V_(SUPP) on the supercapacitorsC2, C4 falls below minimum threshold. When the voltage V_(SUPP) on thesupercapacitors C2, C4 falls below the minimum threshold, the latchcircuit may turn on Q3, thereby removing the power draw from thesupercapacitors to the power converter circuit 216.

The minimum threshold may be set to maintain a maximum power transferfrom the photovoltaic cell 405 to the supercapacitors C2, C4 such thatthe supercapacitors may not discharge below the optimum maximum powertransfer range. For example, the minimum threshold may be set to 4.2V.When the voltage on the supercapacitors C2, C4 exceeds a maximumthreshold (for example, 4.9V), the latch circuit may be engaged throughthe clamp circuit described previously, where the adjustable shuntregulator VR1 turns on the transistor Q7 thereby triggering thetransistor Q11 of the latch circuit.

The capacitor C6 may protect the latch circuit from noise and falselatches. The capacitor C6 may have a capacitance of 0.1 microfarads(μF), for example. When the transistor Q11 is conducting current, thetransistor Q9 may also conduct current, which drives the transistor Q11to remain on, or latched. When sunlight, for example, is not availableto charge the photovoltaic cell 405 (e.g., the photovoltaic cell currentgeneration is minimal), the latch circuit may draw a small amount ofcurrent from the supercapacitors C2, C4 through the path defined by theresistor R9, the transistor Q9, and the resistor R13, in order tomaintain the transistor Q11 in the latched state. Therefore, theresistance of the resistor R9 should be selected to be sufficientlylarge to limit the current draw so as not to drain the supercapacitorsC2, C4. For example, the resistor R9 may have a resistance of 400 KΩ.

The latching circuit may be characterized by an unlatching voltageV_(unlatch), which may be defined as the supplemental supply voltageV_(SUPP) (that is, the voltage across the supercapacitors C2, C4) atwhich the transistor Q11 transitions from an “on” (or latched state) toan “off” (or unlatched state). The unlatching voltage V_(unlatch) may becalculated according to the following example equation:

$V_{unlatch} = \left\lbrack {{\frac{V_{{BE},{Q\; 11}}}{R_{13}} \cdot R_{9}} + V_{{CE},{Q9}} + V_{{BE},{Q11}}} \right\rbrack$

where V_(BE,Q11) is the voltage across the base-emitter junction of thetransistor Q11 when the transistor Q11 is conducting (also the voltageacross the resistor R13); R₁₃ and R₉ are the resistances of theresistors R13, R9, respectively; and V_(CE,Q9) is the voltage across thecollector-emitter junction of the transistor Q9 when the transistor Q9is conducting current. The unlatching voltage V_(unlatch) is equal tothe minimum supplemental supply voltage required to maintain the latchcircuit in the latched state. The unlatching voltage V_(unlatch) may beselected to be equal to the minimum threshold of the supercapacitors C2,C4. For example, the unlatching voltage V_(unlatch) may be approximately4.2V. The unlatching voltage V_(unlatch) may be set by setting theresistance of the resistors R9 and R13 to appropriate values. Forexample, the resistance R13 of the resistor R13 may be 56 KΩ to set theunlatching voltage V_(unlatch) to 4.2V if the collector-emitter voltageV_(CE,Q9) is 0.1V, the base-emitter voltage V_(BE,Q11) is 0.5V, and theresistance R₉ of the resistor R9 is 400 KΩ.

Additional circuit elements may be added to increase the functionalityof the latch circuit. For example, a diode D6 may be included in thelatch circuit to prevent reverse-biasing of the base-emitter junction ofthe transistor Q9.

When the voltage V_(SUPP) on the supercapacitors C2, C4 falls below theminimum threshold (e.g., V_(SUPP) is less than the unlatching voltageV_(unlatch)), the transistor Q11 may stop conducting current. Forexample, when the voltage of the supercapacitors C2, C4 falls below theminimum threshold (e.g., 4.2 volts), power may be provided to the powerconverter circuit 216 from the battery 204. The battery 204 may beconnected to the power converter circuit through an electronic switch,e.g., a FET Q3, and a diode D2. The diode D2 may act to protect thecircuit from reverse voltage, for example, if a user has inserted thebatteries backwards in a battery holder. The battery 204 may providevoltage to the buck converter circuit when the supercapacitors C2, C4contain an insufficient amount of energy.

When the transistor Q11 turns off, the collector-emitter junction of thetransistor Q11 may have a high impedance. The high impedance of thetransistor Q11 across the collector-emitter junction may cause the gateof the FET Q1 to be biased high by the resistor R15, which effectivelypulls up the gate voltage of the FET Q1 to approximately the batteryvoltage V_(BATT) of the battery 204. The FET Q1 may then beginconducting when the transistor Q11 turns off. The resistance of theresistor R15 may be selected to be a sufficiently high resistance so asnot to drain the battery when the FET Q11 is conducting. For example,the resistor R15 may have a resistance of 2.2 MΩ. Likewise, the resistorR17 may also have a high resistance to not drain the battery 204 whenthe FET Q1 is conducting. For example, the resistor R17 may have aresistance of 1 MΩ.

The transistor Q1 may be an enhancement mode n-channel metal oxidesemiconductor field effect transistor (NMOS FET). When the FET Q1 turnson and begins conducting current, the gate of the FET Q3 may be pulleddown to circuit common. The FET Q3 may then begin conducting current,providing current from the battery 204 to the power converter circuit216. Diode D4 may prevent current from the batteries charging thesupercapacitors C2, C4 when Q3 is on. The electrical load two (i.e., thecontrol circuit 208 and the communication circuit 226) may remainpowered by the battery 204 until the voltage on the photovoltaic cell405 exceeds the maximum threshold, thereby engaging the clamp circuit toenable Q7 to turn on, which turns on Q11 and enables the latchingcircuit. When the latching circuit is enabled, the gate of Q1 is pulledto circuit common, turning off Q1, which turns off Q3, such that thebattery 204 is no longer providing power to the power converter circuit216.

The configuration of device 400 is an example, and other exampleconfigurations are possible. In addition, although device 200 and device400 are described herein as including a voltage monitor for monitorcircuit 218, as described previously, a current monitor mayalternatively be used.

FIG. 5 is a block diagram of another example device 500. Device 500 maybe similar to device 200 of FIG. 2, in that the device 500 may have abattery and/or battery housing 504 and a supplemental power source 502(such as a solar cell, for example). However, unlike device 200, device500 may contain two supplemental power supplies for storing energy fromthe energy storage device, as will be described herein. It should benoted that the thick lines shown denote power connections, which aredistinguished from the thinner lines which denote communication lines.

The device 500 may be connected to and provide power to a firstelectrical load 506. For example, the electrical load 506 may include aH-Bridge motor drive circuit and a motor for driving a fabric of amotorized window treatment. Alternatively, the electrical load 506 maybe a sensor, such as a daylight or occupancy sensor, a remote control,an HVAC load, etc. The device 500 many also contain a second electricalload 525. The electrical load 525 may be an internal electrical load.For example, the electrical load 525 may include internal circuitry suchas a control circuit 508 and a communication circuit 526. The electricalload 525 comprising the communication circuit and the control circuitmay handle the communication and power management of the device 500, aswell as the functions of the electrical load 506.

The device 500 may contain a battery and/or battery housing 504. Thebattery may be contained within the battery housing, which may beintegrated into the device 500 or may be external to the device 500. Thebattery 504 of the device 500 may provide power to either or both of thefirst electrical load 506 and the second electrical load 525. Forexample, similar to device 200 shown in FIG. 2, the battery 504 ofdevice 500 may provide a voltage V_(BATT) to power the electrical load506 through path B. The battery 504 may alternatively or additionallyprovide power to the electrical load 525 through path A, as will bediscussed in greater detail herein.

As described, the device 500 may contain a supplemental power source502. The supplemental power source may be, for example, a photovoltaiccell. Other examples are possible.

The supplemental power source of the device 500 may provide power to afirst and/or a second energy storage device, such as first energystorage device 512A and second energy storage device 512B as shown inFIG. 5. The first and second energy storage devices 512A, 512B, mayprovide power to one or both of the electrical load 506 and theelectrical load 525. That is, the supplemental power source 502 mayprovide power to either or both of the electrical load 506 and/or theelectrical load 525 via the first and second energy storage devices 512Aand 512B, as will be described in greater detail herein.

Power may be provided to the electrical load 525 (i.e., the controlcircuit 508 and the communication circuit 526) via a power rail V_(CC).The power rail V_(CC) may be provided through a first power convertercircuit 516A. The first power converter circuit 516A may receive powerfrom an output switch 514B, which may control the source of the powerprovided to the first power converter circuit 516A by switching betweeneither of the first energy storage device 512A and the battery 504. Thatis, the output switch 514B may change state (or position) to change thesource of power provided to the first power converter circuit 516A. Whenthe output switch 514B is in a first state (or first position), thebattery 504 may provide power to the voltage rail V_(CC) through path Athrough the output switch 514B as shown, to the first power convertercircuit 516A, and then to the electrical load 525. For example, when theoutput switch is in a second state (or in a second position), the firstenergy storage device 512A may provide power to the voltage rail V_(CC),thereby powering the electrical load 525 through the first powerconverter circuit 516A.

The first power converter circuit 516A may condition the power receivedfrom the output switch 514B to provide an appropriate amount of power tothe power rail V_(CC) for powering the control circuit 508 and thecommunication circuit 526 of the electrical load 525. For example, thebattery 504 may provide a voltage which may exceed a voltage thresholdV_(CCmax) for the electrical load 525. For example, the battery 504 mayprovide a voltage of 5V or 6V, as required by the motor, while theelectrical load 525 may only need power rail V_(CC) voltage of 2.5V or3V. When the power received by the output switch 514B has a voltage thatis too high for control circuit 508 and/or the communication circuit 526(i.e., the received voltage exceeds V_(CCmax)), the first powerconverter circuit 516A may reduce the voltage received by the outputswitch. For example, the first power converter circuit 516A may be abuck converter. The buck converter may reduce the voltage received bythe output switch 514B to a lower level, such as 2.5V or 3V whenV_(CCmax) is 3.5V, for example. Alternatively, the power convertercircuit 516A may be a linear regulator, a resistor-divider circuit,etc.; however, one will understand these alternate components mayconsume more power than a buck converter.

As previously described, the device 500 may further contain a first anda second energy storage device, 512A, 512B, respectively, for storingpower provided by the supplemental power source 502. The first andsecond energy storage devices may be capacitors, such assupercapacitors, for example, similar to the energy storage device 212of FIG. 2. Alternatively, the first and second energy storage devicesmay be rechargeable batteries, or any other electrical energy storagedevice.

The supplemental power source 502 may provide power to one or both ofthe first and second energy storage devices 512A, 512B via an inputswitch 514A. The input switch 514A may change state (or position) tochange which energy storage device receives power from the supplementalpower source. For example, when the input switch 514A is in a firststate (or first position), the supplemental power source 502 may providepower to the second energy storage device 512B. For example, when theinput switch 514A is in a second state (or second position), thesupplemental power source 502 may provide power to the first energystorage device 512A (i.e., to charge the first energy storage device).According to this configuration, the input switch 514A may only alloweither the first or the second energy storage device to receive powerfrom the supplemental power source. That is, the first and second energystorage devices may not simultaneously receive power from supplementalpower source.

The device 500 may contain a first energy storage device 512A and asecond energy storage device 512B. The first and second energy storagedevices 512A, 512B may be monitored by first and second monitor circuits518A, 518B, respectively. Although not shown, the first and secondmonitor circuits may communicate with the control circuit 508.Additionally or alternatively, the first and second monitor circuits518A, 518B may be integrated with the control circuit 508. For example,the first and second monitor circuits 518A, 518B may each be ananalog-to-digital (A/D) port on the control circuit. Or, the first andsecond monitor circuits 518A, 518B may comprise standalone circuitry.

The first energy storage device 512A may be monitored by the firstmonitor circuit 518A. The first monitor circuit 518A may monitor avoltage or energy level of the first energy storage device 512A. Forexample, the first monitor circuit 518A may monitor a voltage level V1of the first energy storage device 512A. The first monitor circuit 518Amay further control one or more switches 514A, 514B in response to themeasured voltage or energy level, as will be discussed in greater detailherein. For example, the first monitor circuit 518A may monitor thevoltage of the first energy storage device 512A and compare the measuredvoltage V1 to one or more thresholds. Based on the comparison, the firstmonitor circuit 518A may provide a control signal to the input switch514A to change the state of the input switch, allowing power from thesupplemental power source 502 to be provided to either the first energystorage device 512A or the second energy storage device 512B. The firstmonitor circuit 518A may act to maintain an optimal voltage level of thefirst energy storage device 512A, as will be described in greater detailherein.

In a second example, when the first monitor circuit 518A compares themeasured voltage V1 to one or more thresholds, based on the comparison,the first monitor circuit 518A may provide a control signal to theoutput switch 514B to change the state of the output switch 514B. Forexample, the first monitor circuit 518A may monitor the voltage on thefirst energy storage device 512A and may determine whether the voltagedrops below a first threshold. In response to determining that thevoltage on the first energy storage device 512A has dropped below thefirst threshold, the monitor circuit 518A may provide a control signalto the output switch 514B to change the state of the output switch 514B,allowing power from the battery 504 to be provided to the first powerconverter circuit 516A.

If the voltage V1 exceeds the first threshold, and further exceeds asecond threshold greater than the first threshold, the first monitorcircuit 518A may further change the state of the input switch 514A tothe first state to provide power to the second energy storage device512B from the supplemental power source 502. This and other exampleswill be discussed in greater detail herein.

The second energy storage device 512B may receive power from thesupplemental power source 502 when the input switch 514A is in a firststate (or first position) as previously described. The energy stored inthe second energy storage device 512B may be used to power theelectrical load 506 through a second power converter circuit 516B. Thesecond power converter circuit 516B may have an output voltage V_(OUT).The second power converter circuit 516B may be a boost circuit, forexample. The boost circuit may increase, or boost, a voltage V2 suppliedby the second energy storage device 512B, such that the output voltageVOUT exceeds a voltage V_(BATT) supplied by the battery 504. When theoutput voltage VOUT exceeds V_(BATT), the battery 504 may ceaseproviding power to the electrical load 506, and the second energystorage device 512B may provide power to the electrical load 506. Thisis depicted through the use of two diodes, however, one will understandthat active circuitry such as an active switch may alternatively be usedto switch the power supplied to the electrical load 506 from V_(BATT) toV_(OUT), and vice versa.

The device 500 may have a second monitor circuit 518B to monitor thesecond energy storage device 516B. The second monitor circuit 518B maymonitor a voltage, for example, an amount of voltage V2 on the secondenergy storage device 512B, and may enable or disable the second powerconverter circuit 516B based on the amount of voltage on the secondenergy storage device 512B. For example, the second energy storagedevice 512B may only power the electrical load 506 when the secondenergy storage device 512B contains a sufficient amount of power. Inthis way, the device 500 may either enable or disable the second powerconverter circuit 516B to selectively power the electrical load 506 fromthe second energy storage device 512B based on the voltage level of thesecond energy storage device 512B, as monitored by the second monitorcircuit 518B.

As described, the second monitor circuit 518B may monitor the voltage V2on the second energy storage device 512B and may communicate themeasured voltage V2 to the control circuit 508. Based on the receivedcommunication from the second monitor circuit 518B, the control circuitmay compare the voltage with a third and a fourth threshold to determinewhether the voltage exceeds the third and/or the fourth threshold. Basedon the determination, the control circuit may determine whether thesecond power converter circuit 512B should be enabled or disabled (i.e.,whether the second energy storage device 512B contains sufficientcharge, as measured by the amount of voltage V2). For example, if thecontrol circuit 508 determines that the voltage V2 is less than thethird threshold, the second power converter circuit 516B should remaindisabled to allow the battery to power the second electrical load. If,however, the control circuit 508 determines that the voltage V2 on thesecond energy storage device exceeds the third and the fourth threshold,the control circuit 508 may determine to enable the second powerconverter circuit 516B to allow the electrical load 506 to be powered bythe second energy storage device 512B, instead of the battery 504. Thethird threshold may be set such that when the second power convertercircuit 516B is enabled, the voltage output by the second powerconverter circuit V_(OUT) exceeds the voltage V_(BATT), thereby allowingthe second energy storage device to provide power to the electrical load506 instead of the battery 504, as previously described.

In response to the determination that the second power converter circuit516B should be enabled or disabled, the control circuit 508 maycommunicate via one or more messages to the second monitor circuit 518Bto enable or disable the second power converter circuit 516B. Inresponse to the communication, the second monitor circuit 518B mayenable or disable the second power converter circuit 516B. For example,when the voltage V2 measured by the monitor circuit 518B exceeds thefourth threshold, the control circuit 508 may communicate to the secondmonitor circuit 518B to enable the second power converter circuit 516B.The second monitor circuit 518B may then enable the second powerconverter circuit, thereby powering the electrical load 506 from thesecond energy storage device 512B. Although not shown, one willunderstand additional drive circuitry, for example, a motor drivecircuit, may be included to drive the electrical load, as previouslydescribed.

FIGS. 6A-6C depict example flowchart diagrams of methods which may beexecuted by the first and/or second monitor circuits 518A, 518B tocontrol the switches 514A, 514B, and the second power converter circuit516B. FIGS. 7A, 7B show example voltages over time for the first and thesecond energy storage devices 512A, 512B, which will be described intandem with FIGS. 6A-C. For this example, the input switch 514A maystart in the second state, wherein the supplemental power source 502 mayprovide power to the first energy storage device 512A. Further, theoutput switch 514B may start in the first state, where the battery 504may provide power the first power converter circuit 516A. Additionally,the second power converter circuit 516B may be disabled. Hence, thevoltage V1 of the first energy storage device 512A may be increasing atpoint 702A of FIG. 7A as the first energy storage device receives powerfrom the supplemental power source, and no output power of the firstpower converter circuit 516A is provided. Correspondingly, the voltageV2 of the second energy storage device may remain substantially constantat point 702B as the second energy storage device 512B does not receivepower from the supplemental power source 502, nor provides power to thesecond power converter circuit 516B.

The first and second monitor circuits may sample, or measure, thevoltages V1, V2 respectively. For example, the first and second monitorcircuits may sample the voltage periodically, for example, once everymillisecond. Each time the first and/or second monitor circuits samplethe voltage V1 and/or V2, one or more of the methods 6A-C may beexecuted. The times T1, T2, T3, T4, T5, and T6 may indicate exampletimes when the methods 6A-C may be executed. One will understand thattimes T1-T6 are provided for illustration purposes only, that is, themethod may be executed much more frequently than just those times shown.

For example, in FIG. 7A, at time T1, method 6A may be implemented by thefirst monitor circuit 518A. The method 600A of FIG. 6A may start at step602 by the first monitor circuit 518A measuring the voltage V1 of thefirst energy storage device 512A. At step 604, the first monitor circuit518A may determine whether the voltage V1 is below a first threshold.The first threshold may be set to allow the first power convertercircuit 516A to maintain power to the V_(CC) rail to power theelectrical load 525. For example, if the electrical load 525 requires aminimum voltage input of 2.5V, the first threshold may be set to 3V toensure that no interruption of power to the electrical load 525 isexperienced.

At time T1, the first monitor circuit 518A may determine that thevoltage V1 is below the first threshold. The method may then proceed tostep 606 where the first monitor circuit 518A may change the state ofthe output switch 514B to the first state (if the output switch 514B isnot already in the first state), to provide power to the first powerconverter circuit 516A via the battery 504. The first monitor circuit518A may then change the state of the input switch 514A to the secondstate (if necessary) to ensure that the first energy storage device 512Ais being charged by the supplemental power source. The method may thenend.

The voltage V1 on the first energy storage device 512A may begin to riseas power is received from the supplemental power source 502. At point702A, the voltage V1 may reach and exceed the first threshold. At timeT2, the method 600A of FIG. 6A may again execute, and the first monitorcircuit 512A may again measure the voltage V1 at step 602. The firstmonitor circuit 518A may then determine at step 604 that the voltage V1exceeds the first threshold. The first monitor circuit 518A may thenfurther determine whether the voltage V1 exceeds a second threshold atstep 610 of method 600A. The second threshold may be, for example, 4.5V.After determining that the voltage V1 does not exceed the secondthreshold, the method may then exit.

At time T3, the method 600A may again execute, this time through steps602, 604, and 610 as described. At step 610, the first voltage monitorcircuit 518A may determine that the voltage V1 exceeds the secondthreshold. When the voltage V1 exceeds the second threshold, the firstenergy storage device may contain sufficient power (i.e., adequatevoltage) to provide power the first power converter circuit 516A,instead of relying on the battery 504. In response to determining thatthe voltage V1 exceeds the second threshold, the first voltage monitorcircuit 518A may change the state of the output switch 514B to thesecond state at step 612, which may allow the first energy storagedevice 512A to provide power to the first power converter circuit 516A.Correspondingly, the voltage V1 may being to decrease after time T3.

The first monitor circuit 518A may further change the state of the inputswitch 514A to the first state at step 614, which may allow thesupplemental power source 502 to begin charging (i.e., providing powerto) the second energy storage device 512B. The voltage V2 on the secondenergy storage device 512B may then begin to increase at point 704B. Themethod 600A may then end.

As is apparent, the first monitor circuit 518A may affect the voltage V1by controlling the power provided to the first energy storage device512A through the input switch 514A, and controlling the power providedby the first energy storage device 512A through the output switch 514B.Additionally, the first monitor circuit 518A may further impact thevoltage V2 on the second energy storage device by determining when poweris provided to the second energy storage device 512B through control ofthe input switch 514A. The voltage V2 of the second energy storagedevice may additionally be impacted by whether or not power is providedto the second power converter circuit 516B, i.e., whether or not thesecond power converter circuit is enabled. The second monitor circuit518B may control whether or not the second power converter circuit 516Bis enabled, and therefore, may control the discharge of voltage V2 onthe second energy storage device 512B. The second monitor circuit mayperiodically execute method 600C to measure the voltage V2 and determinewhether or not to enable the second power converter circuit 516B.

For example, the second monitor circuit 518B may execute the method 600Cof FIG. 6C at time T4. The method 600C may begin at step 630 bymeasuring the voltage V2. At step 632, the second monitor circuit 518Bmay determine whether the voltage V2 is below a third threshold. Thethird threshold may be, for example, 3.5V. When the voltage V2 is belowthe third threshold, the voltage V2 may be too low to provide sufficientpower to the power converter circuit 516B to allow the output powerV_(OUT) to exceed the battery voltage V_(BATT). The second monitorcircuit 518B may then clear a flag at step 634 and disable the secondpower converter circuit 516B at step 640. For example, the secondmonitor circuit may communicate with the control circuit 508 to set,clear, or determine the status of the flag. The control circuit 508 maystore the state of the flag in memory. The method may then end.

If, at step 632, the voltage V2 is greater than or equal to the thirdthreshold, the second monitor circuit 518B may then compare the voltageV2 to a fourth threshold and determine whether the voltage V2 exceedsthe fourth threshold at step 636. The fourth threshold may be, forexample, 4.5V. If the voltage V2 exceeds the fourth threshold, thesecond monitor circuit may then communicate with the control circuit 508to set the flag at step 642. The second monitor circuit 518B may thendetermine whether or not the electrical load 506 is on at step 644.

If, however, at step 636 the voltage V2 does not exceed the fourththreshold, the second monitor circuit 518B may then determine whether ornot the flag has been set. If the flag has not been set, the secondmonitor circuit may ensure that the second power converter circuit 516Bis disabled at step 640. The method may then end. However, if the flaghas been set, the second monitor circuit may determine whether or notthe second electrical load 506 is on at step 644. For example, themonitor circuit may query the control circuit 508 to determine whetherthe electrical load 506 is on. If the electrical load 506 is not on, themethod 600C may again progress to step 640, disable the second powerconverter circuit 516B, and then end. However, if the electrical load506 is on, the second monitor circuit 518B may enable the second powerconverter circuit at step 646. The method may then end.

Setting the flag at step 642 after the voltage V2 exceeds the fourththreshold may allow the second power converter circuit 516B to beenabled (i.e., to power the load 506) while the voltage V2 on the secondenergy storage device 512B remains above the third threshold and theelectrical load 506 is on. For example, in FIG. 7A, when the voltage V2on the second energy storage device reaches/exceeds the fourth thresholdat point 706B, assuming the electrical load is on at step 644 of method600C, the second power converter circuit 516B may be enabled (see step646 of FIG. 6C). That is, the second power converter circuit 516B may beenabled to provide power to the electrical load 506 even when thevoltage V2 is below the fourth threshold, provided V2 exceeds the thirdthreshold.

From point 706B to point 708B, the voltage of V2 may remain essentiallyconstant. For example, the second energy storage device may power theelectrical load 506 and may also receive power (i.e., may be charging)from the supplemental power source 502 during this time period.

At time T5 the method 600A may again execute. The results may be thesame as when the method was executed at time T4. At time T6, the method600A may again execute. As the voltage V1 at point 708A has nowdischarged to a minimum level (i.e., V1 is less or equal to the firstthreshold), the first monitor circuit 518A may change the state of theinput switch 514A to the second position to charge the first energystorage device 512A, as described in method 600A of FIG. 6A.Correspondingly, after point 708B at time T6 the voltage V2 may begin todecrease as power is supplied from the second energy storage device 512Bto the second power converter circuit to power to the electrical load506, and while the supplemental power source 502 is charging the firstenergy storage device 512A (i.e., the second energy storage device isnot receiving power from the supplemental power source). When thevoltage V2 drops below the third threshold, or when the voltage V2 isbetween the third and fourth threshold while the electrical load 506 isoff, the second power converter circuit 516B may be disabled, and thevoltage V2 may again remain essentially constant.

FIG. 7B is an alternate example of voltages V1, V2 over time while thefirst and second monitor circuits use methods 600B and 600C of FIGS. 6B,6C, respectively. Method 600B may contain similar steps to method 600Aof FIG. 6A, and may be executed by the first monitor circuit 518A. Themethod 600B may contain additional steps 616-622, which may allow thefirst energy storage device 512A to start charging at an earlier time byproviding an additional threshold by which to compare the voltage andcontrol the input switch 514A. For example, FIG. 7B may include a fifththreshold for voltage V1. The fifth threshold may be greater than thefirst threshold and less the second threshold. For example, the fifththreshold may be set to 3.75 V, which is halfway between the first andsecond thresholds. Other examples are possible. The fifth threshold maybe set to establish priority between the first and second energy storagedevices to determine which energy storage device should receive powerfrom the supplemental power source.

The execution of method 600B at time T1 may be the same as previouslydescribed. At time T2, the first monitor circuit 518A may measure thevoltage V1. The first monitor circuit 518A may then compare the measuredvoltage V1 to the first threshold at step 604 and determine that V1exceeds the first threshold. The method may then proceed to step 610,where the first monitor circuit 518A may compare the measured voltage V1to the second threshold and determine that V1 does not exceed the secondthreshold. At step 616, the first monitor circuit 518A may then comparethe voltage V1 with the fifth threshold and determine that V1 doesexceed the fifth threshold. The method 600B may then end, and the inputswitch 514A may remain in the second state (i.e., the first energystorage device may continue to receive power from the supplemental powersource 502). The execution of method 600B at time T3 may be the same aspreviously described.

At time T4, the method 600B may again execute. The first monitor circuit518A may measure the voltage V1 at step 602 and determine at step 604that the voltage V1 exceeds the first threshold. The first monitorcircuit 518A may further determine at step 610 that the voltage V1 doesnot exceed the second threshold. At step 616, the first monitor circuit518A may determine that the voltage V1 exceeds the fifth threshold. Themethod may then end. At the same time T4, or near the time T4, thesecond monitor circuit may execute method 600C as previously described.If the electrical load 506 is on, the second power converter circuit maybe enabled to power the electrical load 506, and the voltage V2 mayremain essentially constant.

At time T5, the first monitor circuit 518A may again execute the method600B through steps 602, 604, and 610. At step 616, the first monitorcircuit 518A may determine that V1 is now below the fifth threshold(i.e., does not exceed the fifth threshold). In response to determiningthat V1 is below the fifth threshold, the first monitor circuit 518A maychange the state of the input switch 514A to the second state, ifnecessary, to ensure that the first energy storage device 512A ischarging. At point 710A, the voltage V1 may begin to increase as thefirst energy storage device 512A receives power from the supplementalpower source 502. Correspondingly, the voltage V2 on the second energystorage device 512B may begin to decrease as power is no longer suppliedfrom the supplemental power source 502 to the second energy storagedevice 512B (while the second energy storage device 512B is supplyingpower via the enabled second power converter circuit 516B to theelectrical load 506). One will understand that if the electrical load506 is not on, according to method 600B, the voltage V2 on the secondenergy storage device 512B will not be decreasing after point 710B, asthe power loss from the second energy storage device 512B providingpower to the second power converter circuit 516B is substantiallyminimal.

FIG. 8 shows a device 800 which is an example implementation of device500 of FIG. 5. The monitor circuits 518A, 518B of FIG. 5 (in thisexample a voltage monitor circuit) are integrated into a control circuit808 of FIG. 8. The input switch 514A of FIG. 5 is depicted in schematicform as the transistors Q81, Q82 of FIG. 8. The output switch 514B ofFIG. 5 is depicted as the transistors Q83, Q84 of FIG. 8. Device 800further includes components shown in FIG. 5 such as: the supplementalpower source 502 (shown in this example as photovoltaic cell 805); thefirst and second energy storage devices 512A, 512B (e.g., shown in thisexample as energy storage device 812A consisting of supercapacitors C5,C6, and energy storage device 812B consisting of supercapacitors C7, C8,respectively); the first and second power converter circuits 516A, 516Bcorresponding to 816A, 816B; the battery 504 (corresponding to thebattery 804 shown in FIG. 8); and the first electrical load 506, and thesecond electrical load 525 corresponding to electrical load 806, 825,respectively.

All voltages described in FIG. 8 are measured with reference to circuitcommon, shown as 803. The transistors Q81, Q82, Q83, and Q84 may all bep-channel metal oxide semiconductor field-effect transistor (PMOS FET),for example, as shown. The control circuit 808 which acts as the firstand second monitor circuits to monitor the voltage V1, V2 of the firstand second energy storage devices, respectively as shown, may be thesame as the control circuit of electrical load 825, or may be adifferent control circuit.

For example, the control circuit 808 may be the same control circuit ofthe electrical load 825. The electrical load 825 may further include acommunication circuit, as shown in FIG. 5. The communication circuit maybe integrated with the control circuit 808, or may be a separatecircuit.

One will understand that the voltages V1, V2 need not be the samevoltage, and that the control circuit 808 may prioritize which energystorage device has the most charge. For example, the first energystorage device may have a higher priority than the second energy storagedevice as the first energy storage device may allow the device 800 tocontinue to power the electrical load 825, thereby allowing the device800 to continue to communicate and report issues.

The circuit shown may set the impedance for the photovoltaic cell 805.Voltage to the electrical load 825 (e.g., a control circuit, acommunication circuit, and/or other low voltage circuitry) may beprovided by the first power converter circuit 816. The first powerconverter circuit 816A may be a buck circuit, for example.Alternatively, the first power converter circuit 816A may be a linearregulator, voltage divider, or the like. The first power convertercircuit 816A may reduce the voltage from the battery 804 or first energystorage device 812A to the appropriate level for powering the secondelectrical load 825 as described previously. For example, the batteryvoltage V_(BATT) may be any voltage between and/or including 6-9V. Forexample, the voltage V1 on the first energy storage device may be anyvoltage between and/or including 3-5V. According to this example, thefirst power converter circuit 816A may reduce the voltage V1 and/or thevoltage V_(BATT) to an output voltage V_(CC) of approximately 2.5V. Onewill understand that the exact voltages used may be specific to thecontrol circuit selected, the capacitors C5, C6, and the battery 804.

The second power converter circuit may contain an enable/disable line818. The control circuit 808 may enable or disable the second powerconverter circuit 816B through an enable/disable line 818. For example,the second power converter circuit 816B may be a boost converter. Theboost converter may boost the voltage V2, which may be within the rangeof 3.5-5V, to the voltage V_(OUT) at 12V.

Voltage to the electrical load 806 may be provided by the second powerconverter circuit 816B when the output voltage VOUT exceeds the batteryvoltage V_(BATT), through the use of diodes D3, D5. The diodes D1-D5shown may be low power loss diodes, for example, Schottky diodes. VOUTmay be greater than V_(BATT) when the second power converter circuit816B is on, that is, enabled. For example, when the second powerconverter circuit 816B is enabled, the voltage VOUT may be 12V, whilethe voltage V_(BATT) may be 6-9V. Power may then be provided to thesecond electrical load 806 by the second energy storage device (i.e.,the supercapacitors C7, C8). Alternatively, one will recognize that D3and D5 may be replaced with an active switch to achieve the samefunction.

The control circuit may monitor the voltage V1, V2 via two or moreanalog to digital (A/D) lines shown as 820A, 820B, respectively. Thecontrol circuit 808 may use the measured voltages V1, V2 to determinewhether or not to enable the second power converter circuit 816B, aspreviously described.

The control circuit 808 may change the state of the switches Q81, Q82(which comprise the input switch), based on the voltages V1, V2. Forexample, the control circuit may control a gate voltage 822A, 822B toturn the transistors Q81, Q82 on or off, respectively. The controlcircuit 808 may further ensure that only one of Q81 and Q82 is turned onat the same time (i.e., only the first energy storage device 812A or thesecond energy storage device 812B is charging). The capacitors C5-C8 maybe similar to capacitors C2, C4 of FIG. 4. For example, capacitors C5-C8may be supercapacitors.

The control circuit 808 may change the state of the switches Q83, Q84(which comprise the output switch), based on the voltages V1, V2. Forexample, the control circuit may control a gate voltage 824 to turn theFETs Q83, Q84 on or off, respectively. An inverter 826, or other controlcircuitry establishing the same type of function, may be used to providea complementary drive signal to the gate of the FET Q84. For example,the inverter 826 may be used to invert the signal 824 such that the gatesignal provided to the FET Q84 is the inverted signal provided to theFET Q83. The inverter 826 may ensure that only one of FET Q83, Q84 is onat a time, that is, Q83 and Q84 may not both be on simultaneously. Thecontrol circuit 808 may use the gate drive signal 824 and the FETs Q83,Q84, to control power to the first power converter circuit 816A. Forexample, when the control circuit sends a gate signal 824 to turn on FETQ83 (thereby turning off FET Q84), the first energy storage device 812Amay provide power via voltage V1 to the first power converter circuit.Alternatively, a diode may be used in place of FET Q83.

When the gate drive signal 824 of the control circuit 808 turns off FETQ83 (thereby turning on FET Q84), the battery 804 may provide power tothe first power converter circuit 816A through the FET Q84 and the diodeD4. The FET Q84 may be rendered conductive to provide the batteryvoltage V_(BATT) from the battery 804 when the energy storage device812A does not have sufficient charge to provide power to the first powerconverter circuit 816A, e.g., when the magnitude of the supplementalsupply voltage V₁ stored by the energy storage device 812A is below thefirst threshold (for example, below 3 volts).

The voltages on the first and second energy storage devices may bemaintained at a level greater than 3V to prevent deep discharging of theenergy storage devices. For example, if the first and second energystorage devices are supercapacitors which receive energy from aphotovoltaic cell, the amount of voltage on the first and second energystorage devices may determine the efficiency of power transfer from thephotovoltaic cell to the first and second energy storage devices,respectively. For example, when the voltage V1 or V2 on the first orsecond energy storage device drops below a minimum threshold (forexample, the first and third thresholds previously described, such as3-3.5V), the photocell may no longer be able efficiently charge thefirst and second energy storage devices. That is, the time required forrecharging the first and second energy storage device may greatlyincrease as the voltage V1 or V2 falls below the minimum threshold.

Conversely, the first and second energy storage devices may receivepower from the photocell (i.e., may charge) most efficiently around amaximum threshold, that is, the second and fourth threshold, or around4.5V. However, the voltage V1 or V2 may exceed the maximum threshold forthe circuit shown. As such, a further addition to the circuit of device800 may include a clamp circuit, for example a diode, across the firstand/or second energy storage devices, which may clamp the voltage V1 orV2 to the maximum threshold. For example, a clamp circuit may include adiode across supercapacitor bank 812A with a clamping voltage of 5V.

One will understand that the circuit schematic of device 800 shown inFIG. 8 is for illustration purposes only, and that other circuits may beconstructed which serve the same function. For example, although theFETs Q81-Q84 are shown as PMOS, one will understand that NMOS FETs mayalternatively be used with referencing and biasing updated accordingly.Or, any controllable switching device may be used, such as, for examplebipolar junction transistors. Additionally, a diode may be used in placeof Q83. These and any alternate circuits having the same resultingfunctionality as described herein are also considered as alternativeembodiments.

Although device 400 and 800 have been described as receiving power froma solar cell or PV module, other types of supplemental power sources mayalternatively be used. For example, a wireless RF power source may beused as a supplemental power source. FIG. 9 shows an example userenvironment 900 with a wireless power supply source for powering amotorized window treatment 954 according to another embodiment. Forexample, the motorized window treatment 954 may include a motor driveunit, such as, for example, device 200. The motor drive unit of themotorized window treatment may have a supplemental power source whichreceives power wirelessly (i.e., via RF) to power the electrical load225 (i.e., the control and communication circuits).

The wireless power supply may comprise a wireless power transmittingmodule 990 configured to wirelessly transmit power via RF signals 998 towireless power receiving circuits inside of one or more control devicesin the room including, for example, the motor drive unit of themotorized window treatment 954. The wireless power receiving circuitsmay be configured to harvest energy from the RF signals 998 transmittedby the wireless power transmitting module 990.

The wireless power transmitting module 990 may comprise a wireless powertransmitting circuit (not shown) housed within an enclosure 992 and anantenna (e.g., a dipole antenna) having for example two transmittingantenna wires 994A, 994B that extend from the enclosure 992 and arecoupled (e.g., electrically or magnetically coupled) to the wirelesspower transmitting circuit. The antenna may also be formed as a loop orhelical antenna. The wireless power transmitting module 990 may compriseelectrical prongs (not shown) that may be plugged into a standardelectrical outlet 996 for powering the wireless power transmittingcircuit from an AC power source. The transmitting antenna wires 994A,994B may be positioned horizontally to extend in opposite directions,for example, along the floor at the bottom of a wall below the motorizedwindow treatment 954. For example, the wireless power supplytransmitting module 990 may be configured to continuously transmit powervia RF signals 998 to the wireless power receiving circuits of thesupplemental power supply of the motorized window treatment. Inaddition, the wireless power supply transmitting module 990 may beconfigured to transmit power in a periodic (e.g., a pulsed orpulse-width modulated) manner, for example, in bursts having a higherpeak power for a shorter duration. If power is transmitted in a periodicmatter, the frequency of the pulses can be adjusted with respect to time(e.g., swept), such that there is no specific channel (e.g., frequency)with which the wireless power supply transmitting module 990 isconstantly interfering.

For example, the motorized window treatment 954 may include a motordrive unit 955. The motor drive unit 955 may comprise an internalwireless power receiving circuit that allows for powering a motor, aninternal control circuit, and an internal wireless communication circuit(e.g., an RF transceiver) of the motor drive unit. The motor drive unit955 may comprise an antenna (e.g., a dipole antenna) having two antennawires 956A, 956B that extend from the motor drive unit 955 and areelectrically coupled to the internal wireless power receiving circuitand that are tuned to receive RF signals 998. The antenna may also beformed as a loop or helical antenna. The motor drive unit may controlthe fabric or drapery 952 based on control instructions received from acontrol device 970.

FIG. 10 shows an example supplemental power supply 1020 according to afurther embodiment. The supplemental power supply 1020 is an example ofthe supply that can be used in FIG. 9, and can be used in device 200 asthe element 220. The supplemental power supply 1020 may include asupplemental power source 1002 and an energy storage device 1012. Thesupplemental power source may be a wireless power receiving circuitwhich may receive power from a wireless power supply source, such aswireless power transmitting module 990 of FIG. 9, located remotely fromthe wireless power receiving circuit. The wireless power receivingcircuit may include an antenna 1032, e.g., an electric field (E-field)antenna, a balun circuit 1034, and a radiofrequency to direct current(RF-to-DC) converter circuit 1036. For example, the antenna 1032 maycomprise a dipole antenna.

The energy storage device 1012 may include a capacitor, such ascapacitor 1038 shown in FIG. 10. The capacitor may be a supercapacitor,or may be a tantalum, electrolytic, or other type of capacitor.Alternatively, the energy storage device may comprise an inductor, orother suitable energy storage device. The capacitor 1038 may storeenergy provided by the wireless power receiving circuit and may providevoltage V_(SUPP) to the power converter circuit 216 of device 200 ofFIG. 2. For example, the capacitor 1038 may have a capacitance ofapproximately 100 μF.

The antenna 1032 may capture (e.g., harvest) power from RF signalstransmitted by a wireless power transmitting module (e.g., the RFsignals 998 transmitted by the wireless power transmitting module 990).For example, the amount of power harvested by the antenna 1032 from theRF signals may be approximately 40 mW. The RF-to-DC converter circuit1036 may operate to convert the energy from the RF signals to anun-regulated DC voltage across the storage capacitor 1038. The RF-to-DCconverter circuit 1036 may have, for example, an efficiency ofapproximately 50%, such that the amount of power able to be delivered bythe RF-to-DC converter circuit may be approximately 20 mW.

The power stored by the energy storage device, capacitor 1038, mayprovide a supply voltage V_(SUPP). V_(SUPP) may be supplied to theterminal 224 to provide power to the power converter circuit forpowering the electrical load 225, as shown in FIG. 2.

FIG. 11 is an alternate embodiment of a device 200′. Similarly numberedcomponents correspond to components as described in FIG. 2. For example,the battery 204′ may be the same as battery 204 in FIG. 2. Here, boththe electrical load 206′ and the electrical load 225′ of device 200′ maybe powered by either the battery 204′ or the supplemental power supply220′ by means of the switch 214′. For example, the supplemental powersupply may comprise one or more rechargeable batteries.

FIG. 12 is an example voltage profile over time 1200 of a magnitude of asupply voltage V_(SUPP) represented by the dashed line, and a magnitudeof a battery voltage V_(BATT) represented by the solid line. V_(BATT)may correspond to the voltage on battery 204′, and V_(SUPP) maycorrespond to the voltage of the energy storage device 212′, as shown inFIG. 11. For example, the energy storage device 212′ may be arechargeable battery and the battery 204′ may be a primary (i.e.,non-rechargeable) battery. At time T0, when the switch 214′ is in thesecond position, the energy storage device 212′ may provide power to theelectrical load 206′ and the electrical load 525′. As the energy storagedevice 212′ provides power to the electrical loads, the energy storagedevice 212′ may begin to discharge to the minimum voltage threshold,Vmin.

When the energy storage device 212′ reaches the minimum voltagethreshold Vmin at time T1, the monitor circuit 218′ may detect that thevoltage on the energy storage device 212′ has reached the minimumthreshold Vmin and may change the state of the switch 214′ to the firstposition, thereby providing power to the electrical loads from theprimary battery and allowing the energy storage device 212′ to recharge.For example, the energy storage device 212′ may be recharge via a solarcell, wireless power supply, etc., as previously described. At thistime, the voltage of the primary cell may begin to decrease.

At time T2, the monitor circuit 218′ may detect that the voltage on theenergy storage device 212′ has reached a maximum threshold Vmax. Themonitor circuit may then change the state of the switch 214′ to thesecond position, thereby providing power to the electrical loads fromthe energy storage device, which may further discharge. The process mayrepeat at time T3 when the energy storage device reaches the minimumthreshold, and the monitor circuit again triggers the switch to providepower to the electrical loads via the primary battery 204′.

Although the embodiments described herein are specific to solar cellsand wireless power supplies, one skilled in the art will readilyrecognize that other types of supplemental power sources or energyharvesters could be used. For example, other supplemental power sourcesmay include: thermal energy harvesters, acoustic or vibrational energyharvesters, static electricity energy harvesters, and the like.

While this disclosure has been described in terms of certain embodimentsand generally associated methods, alterations and permutations of theembodiments and methods will be apparent to those skilled in the art.Accordingly, the above description of example embodiments does notconstrain this disclosure. Other changes, substitutions, and alterationsare also possible without departing from the spirit and scope of thisdisclosure.

What is claimed is:
 1. A power distribution control apparatuscomprising: a housing configured to receive a primary energy storagedevice, the primary energy storage device to provide power to anelectrical load operatively coupled to a motorized window treatment; asupplemental power system that includes an energy collection deviceoperatively coupled to a secondary energy storage device; communicationscircuitry selectively, reversibly, transitionable between a SLEEP stateand an ACTIVE state; switching circuitry selectively transitionablebetween a first state and a second state, wherein: in the first statethe switching circuitry operatively couples the communications circuitryto receive power from the supplemental power system; and in the secondstate the switching circuitry operatively couples the communicationscircuitry to receive power from the primary energy storage device;monitor circuitry operatively coupled to the supplemental power system,the monitor circuit to: monitor an electrical parameter of the secondaryenergy storage device; compare the electrical parameter to a firstthreshold value; and responsive to a determination that the electricalparameter is less than the first threshold value, cause the selectivetransition of the switching circuitry from the first state to the secondstate.
 2. The apparatus of claim 1 wherein the monitor circuitry tofurther: compare the electrical parameter to a second threshold value;and responsive to a determination that the electrical parameter isgreater than the second threshold value, cause the selective transitionof the switching circuitry from the second state to the first state. 3.The apparatus of claim 1, further comprising: control circuitrycommunicatively coupled to the communications circuitry, the controlcircuitry to selectively provide power from the primary energy storagedevice to the electrical load; wherein: in the first state the switchingcircuitry further operatively couples the control circuitry to receivepower from the supplemental power system; and in the second state theswitching circuitry further operatively couples the control circuitry toreceive power from the primary energy storage device.
 4. The apparatusof claim 1 wherein the energy collection device comprises a solar energycollection device.
 5. The apparatus of claim 1 wherein the energycollection device comprises a radio frequency energy scavenging device.6. The apparatus of claim 1 wherein the monitor circuitry comprisesvoltage monitor circuitry.
 7. The apparatus of claim 6 wherein theelectrical parameter comprises an output voltage of the supplementalpower system and the first threshold value comprises a minimum operatingvoltage of the communications circuitry.
 8. The apparatus of claim 7wherein the second threshold value comprises an operating voltage of thecommunications circuitry.
 9. The apparatus of claim 6, wherein thevoltage monitor circuit comprises a clamp circuit and a latch circuit.10. The apparatus of claim 9, wherein the clamp circuit and the latchcircuit are configured to maintain the output voltage of thesupplemental power system between a minimum threshold and a maximumthreshold.
 11. The apparatus of claim 10, wherein when the outputvoltage of the supplemental power system exceeds the maximum threshold,the clamp circuit is configured to clamp the output voltage to themaximum threshold.
 12. The apparatus of claim 11, wherein, responsive todetection of an output voltage of the supplemental power system lessthan the minimum threshold: cause the latch circuit to unlatch; andtransition the switching circuitry from the first state to the secondstate responsive to unlatching the latch circuit.
 13. The apparatus ofclaim 1, wherein the secondary energy storage device of the supplementalpower system includes a first energy storage device, the apparatusfurther comprising: a second energy storage device operatively coupledto the electrical load; and a second switch operably connected to thefirst energy storage device and the second energy storage device, thesecond switch reversibly transitionable between a third state and afourth state, such that, in the third state, the second switchelectrically decouples the supplemental power system from the secondenergy storage device and operatively couples the first energy storagedevice to the supplemental power system; in the fourth state, the secondswitch electrically decouples the supplemental power system from thefirst energy storage device and electrically conductively couples thesecond energy storage device to the supplemental power system.
 14. Theapparatus of claim 13, further comprising: a power converter circuit inelectrical connection between the second energy storage device and theelectrical load for providing power from the second energy storagedevice to the electrical load; and a second monitor circuit operablycoupled to the second energy storage device, the second monitor circuitconfigured to: compare a voltage of the second energy storage device toa third threshold; and based on the comparison, enable or disable thepower converter circuit.
 15. The apparatus of claim 14, the secondmonitor circuit to further: enable the power converter circuitresponsive to detection of an output voltage of the power convertercircuit greater than an output voltage of the primary energy storagedevice.
 16. The apparatus of claim 15, the second monitor circuit tofurther: disable the power converter circuit responsive to detection ofthe output voltage of the power converter circuit less than the outputvoltage of the primary energy storage device.
 17. The apparatus of claim13, wherein the second energy storage device includes a supercapacitor.18. The apparatus of claim 1, wherein the electrical load includes amotor configured to adjust a position of one or more motorized windowtreatment components.
 19. The apparatus of claim 1, wherein theelectrical load includes a sensor.
 20. The apparatus of claim 1 whereinthe communications circuitry includes wireless communications circuitrythat periodically transitions between the ACTIVE state and the STANDBYstate to detect a command to change the position of one or moremotorized window treatment components.